1,720,952 research outputs found
Investigation of Lagrangian coherent structures in a wake-induced boundary layer transition
No full textThe evolution of coherent structures in a flat plate boundary layer transition induced by the cylinder wake is investigated using the particle image velocimetry (PIV) technique. The finite-time Lyapunov exponent (FTLE), which characterizes the amount of stretching about the flow trajectory, is used to extract the Lagrangian coherent structures. It is revealed that secondary vortex is induced by the cylinder wake vortices in the near wall region,which would evolve into hairpin vortex as it convects downstream. The subsequent evolvement of the hairpin vortex, characterized by the regeneration of offspring hairpin vortex upstream of it, leads to the appearance of the hairpin packet and the boundary layer finally reaches a turbulent state
Wave turbulence of a rotating array of quantized vortices in the T → 0 temperature limit
No full textThe dynamics of quantized vortices in the zero temperature limit is currently of great interest, particularly in the case of the Fermi superfluid He-B. Here we study wave turbulence, generated by the librating motion of a rotating cylindrical container filled with He-B, in the limit of vanishing viscous forces at temperatures . The polarization of the quantized vortices with respect to the axis of rotation is measured using non-invasive NMR techniques. We observe a decrease of the polarization when the librating motion is started, and a two-stage relaxation process when the modulation of the rotation velocity is stopped. The first relaxation process is associated with the dissipation of large-scale flow stored in inertial waves and the solid body rotation of the vortex array. From the decay of these energy reservoirs we determine the rate of energy dissipation of large-scale flow. The later second process is related to the relaxation of Kelvin waves on individual vortices. This process is monitored by the recovery of the polarization. The existence of a Kelvin wave cascade at the lowest temperatures is currently a central open question. We supply some evidence for the cascade
Phenotypic characterization of the Xenorhabdus bacterial symbiont of a Texas strain of the entomopathogenic nematode Steinernema riobrave, and characterization of the Xenorhabdus bovienii bacterial symbiont of a Newfoundland strain of Steinernema feltiae
No full textTwo bacterial symbionts of entomopathogenic nematodes, one of which originated from Texas, U.S.A., and the other from Newfoundland, Canada, were characterized phenotypically. These strains belonged to the genus Xenorhabdus. The Newfoundland (NF) strain was shown to be X. bovienii but the Texas (TX) strain was not identified at the species level. Four additional cultures of Xenorhabdus were included in the study. These were a strain of X. bovienii (Umea), which was from a nematode of European origin, and strains of X. nematophilus, X.beddingii, and X.poinarii. The tests used in this study indicated identical properties for the NF (North American) and Umea (European) strains of X. bovienii. These could be differentiated from the other strains studied by their failure to grow at 34 degrees C and resistance to low concentrations of a mixture of amoxilline and clavulanic acid. The Xenorhabdus TX strain could be differentiated from the other strains studied by its failure to grow at 10 degrees C. Of the tests done, approximately 30 were useful in distinguishing between the strains and species studied.PT: J; CR: ABUHATAB MA, 1997, J APPL MICROBIOL, V82, P351 AKHURST RJ, 1983, INT J SYST BACTERIOL, V33, P38 AKHURST RJ, 1986, INT J SYST BACTERIOL, V36, P454 AKHURST RJ, 1988, J GEN MICROBIOL 7, V134, P1835 AKHURST RJ, 1990, ENTOMOPATHOGENIC NEM, P75 BOEMARE NE, 1988, J GEN MICROBIOL 3, V134, P751 BOEMARE NE, 1993, INT J SYST BACTERIOL, V43, P249 CABANILLAS HE, 1994, FUND APPL NEMATOL, V17, P219 CABANILLAS HE, 1996, FUND APPL NEMATOL, V19, P273 CABANILLAS HE, 1996, J NEMATOL, V28, P75 DUNPHY GB, 1994, CAN J MICROBIOL, V40, P161 EHLERS RU, 1988, SYST APPL MICROBIOL, V10, P121 FISCHERLESAUX M, 1999, FEMS MICROBIOL ECOL, V29, P149 FISCHERLESAUX M, 1999, INT J SYST BACTERI 4, V49, P1645 FUJIIE A, 1995, APPL ENTOMOL ZOOL, V30, P23 HOLT JG, 1994, BERGEYS MANUAL DETER HOMINICK WM, 1996, BIOCONTROL SCI TECHN, V6, P317 JAGDALE GB, 1996, J NEMATOL, V28, P301 JAGDALE GB, 1997, CAN J ZOOL, V75, P2137 NISHIMURA Y, 1994, WORLD J MICROB BIOT, V10, P207 SMIBERT RM, 1994, METHODS GEN MOL BACT, P607 WOODRING JL, 1988, SO COOPERATIVE SERIE, V331; NR: 22; TC: 2; J9: CAN J MICROBIOL; PG: 5; GA: 335XVSource type: Electronic(1
Retinitis Pigmentosa GTPase Regulator (RPGR) protein isoforms in mammalian retina:insights into X-linked Retinitis Pigmentosa and associated ciliopathies
Full text linkMutations in the cilia-centrosomal protein Retinitis Pigmentosa GTPase Regulator (RPGR) are a frequent cause of retinal degeneration. The RPGR gene undergoes complex alternative splicing and encodes multiple protein isoforms. To elucidate the function of major RPGR isoforms (RPGR 1-19 and RPGR ORF15), we have generated isoform-specific antibodies and examined their expression and localization in the retina. Using sucrose-gradient centrifugation, immunofluorescence and co-immunoprecipitation methods, we show that RPGR isoforms localize to distinct sub-cellular compartments in mammalian photoreceptors and associate with a number of cilia-centrosomal proteins. The RCC1-like domain of RPGR, which is present in all major RPGR isoforms, is sufficient to target it to the cilia and centrosomes in cultured cells. Our findings indicate that multiple isotypes of RPGR may perform overlapping yet somewhat distinct transport-related functions in photoreceptors
Letter from an unknown author to Thomas J. Goree concerning information on specific regimetns and battles in the Civil War.
No full textLetter from an unknown author to Thomas J. Goree asking for information on specific battles and regiments in the Civil War. The author thanks Goree for his reply and agreement to help provide information pertaining to a project the author has taken on. The author expresses that he feels as though he has taken on a much bigger task than he anticipated, and needs as much help as possible in acquiring information
Rent - seeking trade policy : a time series approach
Full text linkUsing a time-series approach, the author analyzes the relationship between the extent of rent-seeking trade policy and both political and economic variables. For rent-seeking trade policy, the indicator he uses is the number of foreign-trade regulations passed each year for the benefit of a single firm or industry. The author uses data from Uruguay for 1925-83. Uruguay, which experienced an impressive economic decline, is an outstanding example of a rent-seeking society. After being a wealthy economy in midcentury, it suffered almost complete stagnation, which led to social and policital disintegration by the end of the 1960s. Three decades of restrictive regulations on foreign trade had created a nearly closed economy by the end of the 1960s. It was worth analyzing whether policymakers'great receptiveness to demands for protection could account for Uruguay's decline. Over the period 1925-83, the author finds almost 4,000 laws, decrees, and administrative resolutions that create, maintain, or modify a foreign-trade regulation for the benefit of a single firm or industry. About half of them explicitly identify the petitioner - usually a firm or guild. Since the size of the Uruguayan economy changed over the period studied, the author scales the annual number of regulations by output or exports to measure the extent of rent-seeking trade policy. The author shows that the extent of rent-seeking trade policy increased with discretionary policies and under dictatorship. (In the period studied, there were two stages of democracy - until 1932 and from 1943-72 - and two stages of dictatorship.) He also shows that rent-seeking trade restrictions increased under import-substitution strategies and, more unexpectedly, under active export promotion. This suggests that discretionary power leads to wasteful distribution, whether it is used to support inward- or outward-oriented policies. Finally, the author analyzes the correlation between innovations in the trade policy indicator and innovations in the growth rates of output and exports, with a lag of up to 20 years. Surprisingly, he finds a positive correlation with output growth rates after two or three years. But the correlation becomes negative some years later, particularly in the case of exports. The short-run positive impact on growth rates, together with the surprisingly long time lag before the negative impact, may account for policymakers'receptiveness to demands for protection.Trade Policy,Achieving Shared Growth,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Environmental Economics&Policies
Big Data, Big Libraries, Big Problems?: the 2014 LibTech Anti-talk?
Full text linkThe desire to create automatons is a familiar theme in human history, and during the age of the Enlightenment mechanical automatons became not only an “emblem of the cosmos”, but a symbol of man’s confidence that he would unlock nature’s greatest mysteries and fully harness her power. And yet only a century later, automatons had begun to represent human repression and servitude, a theme later picked up by writers of science fiction. Man’s confidence undeterred, the endgame of the modern scientific and technological mindset, or MSTM, seems to be increasingly coming into view with the rise of “information technology” in general and “Big data” in particular. Along with those who wield them, these can be seen as functioning together as a “mechanical muse” of sorts – surprisingly alluring – and, like a physical automaton can serve as a symbol – a microcosm – of what the MSTM sees (at the very least in practice) as the cosmic machine, our “final frontier”. And yet, individuals who unreflectively participate in these things – giving themselves over to them and seeking the powers afforded by the technology apart from technology’s rightful purposes – in fact yield to the same pragmatism and reductionism those wielding them are captive to. Thus, they ultimately nullify themselves philosophically, politically, and economically – their value increasingly being only the data concerning their persons, and its perceived usefulness. Likewise libraries, the time-honored place of, and symbol for, the intellectual flowering of the individual, will, insofar as they spurn the classical liberal arts (with the idea that things are intrinsically good, and in the case of humans, special as well) in favor of the alluring embrace of MSTM-driven “information technology” and Big data - unwittingly contribute to their irrelevance and demise as they find themselves increasingly less needed, valued, wanted. Likewise for the liberal arts as a whole, and in fact history itself, if the acid of a “science” untethered from what is, in fact, good (intrinsically), continues to gain strengt
Letter from Caleb Foote to A. J. Muste, April 1, 1942
No full textLetter to A. J. Muste, likely from Caleb Foote, regarding the possibility of Japanese American families resettle in the Midwestern states. Author describes a recent meeting between Joseph R. Goodman, himself, and Milton Stover Eisenhower, Director of the War Relocation Authority, and correspondence with the president of Antioch College. Author writes "I think the three main question the government will ask in any such plan are 1) are defense industries nearby? 2) what will public reaction be? 3) what are the employment opportunities for the Japanese?" Author also describes situation with curfew in San Francisco: "Typical of what is happening: the other night a Japanese doctor came to the YMCA secretary in San Francisco about 7 o'clock. He had a patient that he need to operate on immediately, but a) he couldn't get a hospital in the city to take the patient, and b) in an hour he had to be back in his house til 6 AM because of the curfew, not matter what happened to the patient during thPersonal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
High-resolution extreme ultraviolet spectroscopy of G191-B2B: structure of the stellar photosphere and the surrounding interstellar medium
No full textWe have continued our detailed analysis of the high-resolution (R= 4000) spectroscopic observation of the DA white dwarf G191-B2B, obtained by the Joint Astrophysical Plasmadynamic Experiment (J-PEX) normal incidence sounding rocket-borne telescope, comparing the observed data with theoretical predictions for both homogeneous and stratified atmosphere structures. We find that the former models give the best agreement over the narrow waveband covered by J-PEX, in conflict with what is expected from previous studies of the lower resolution but broader wavelength coverage Extreme Ultraviolet Explorer spectra. We discuss the possible limitations of the atomic data and our understanding of the stellar atmospheres that might give rise to this inconsistency. In our earlier study, we obtained an unusually high ionization fraction for the ionized He ii present along the line of sight to the star. In the present paper, we obtain a better fit when we assume, as suggested by Space Telescope Imaging Spectrograph results, that this He ii resides in two separate components. When one of these is assigned to the local interstellar cloud, the implied He ionization fraction is consistent with measurements along other lines of sight. However, the resolving power and signal-to-noise available from the instrument configuration used in this first successful J-PEX flight are not sufficient to clearly identify and prove the existence of the two components
Dredge, drain, reclaim: The art of a nation
No full textHistorical overview of hydraulic engineering in the Netherlands until 1960. The author wrote the main part of this book during the second world war. The author (1893-1959) advocated at that time strong improvement of the Dutch sea defences, but this was politically not accepted. For that he used the pseudonym "Dr. Cassandra". After 1953 he became the "father" of the Deltaworks, described in the last chapter of this book (which was updated by Stuvel)
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